Thanks H.
The images are in no way debilitating or worrisome -- they just pique my interest. And I looked up afterimages, but there is no causal connection of that type in my experience.
The patches of color tend to happen at any time that I have my eyes open, and are more noticeable when I'm in an environment with a white background, while the sparks of white and blue light can happen whether my eyes are open or closed.
Thanks again